Face plate for electrical contact



Patented Jan. 6, 19311 ctnutnns A; LAISE, or nawonrrtunw JERSEY, ASSIGNOB, Y unsnn ASSIGNMENTS, 'ro- EISLER nrncraro cparonarron, A conronarron or DELAWARE recs sta rs non E Lnormcm. con'rAor No Drawing.

3 i This invention relates ,to-a'n improved contact suitable for X-ray targets, radio targets,

ignition contacts, spark plug points and conand oxidation, and which has a great density and compactness and may be securely mounted in a metal backing.

Contacts heretofore used for the above mentioned purposes have usually'employed a face plate of wrought or malleable tungsten, or of a platinum-iridium alloy. Contacts of pure, wrought tungsten, although they are refractory and have the advantage of a high melting point, are diflicult to unite to a metal backing of copper or equivalent metal and lack compactness, toughness and resistance to pitting. As a result, they are subject to internal heating effects, particularly at the junction of the face plate and the metal backing'and accordingly, to a rapid disintegration.

' An object of my invention is to provide a refractory contact or face plate which avoids these deficiencies andhas a relatively greater compactness and 'res1stanceto dls'lntegratlon 130 than a face plate of pure wrought tungsten.

Other objects of the invention are to provide'a material for contacts which has the desirable refractory qualities but which may be readily-and econpmically formed into the desired shape and securely joined to a suitable backing of a low melting point metal, and to provide a contact which may b'emore readily united in a uniform, intimate union with other metals. l I

' With these and other objects, the invention comprises the contact and 'contact material described and set forth in the followingspe'c i'fication and claims.

In producing my improved contact or face plate I employ an alloy composed of tungsten vanadium and silicon. A small amount of thorium may also be added to the .alloy. Al.- though vanadium and silicon have lower melting points than tungsten, my alloy of tungsten, vanadium and silicon "is harder,

Application filed August 25,1927. Serial No. 215,505.

tougher, and more compact than contactsror I faceplates of pure tungsten andare, therefore, more resistant to disintegration under.

the conditions to which such face platesare subjected. This alloy also has theadvanta-ge of being more easilyworked and of-providing a surface .that may besuperficially alloyed with materials for mounting ona metal backing. r 1

-I produce my alloy by firstpreparing a suitable tungsten base. This is done by-s tart mg wlth tungstic acid which has been purified so that it'is chemically'pure tungsten oxide containing notmore than 25% mineral impurities. Two thousand grams oflthis tungstic acid are dissolved in a mixture of 2000 cc. of C. P. ammonium hydrate having a specific gravity-of .900 and, 5000 cc. of distilled water. After stirring for one-half hour, most of the W0 is dissolved and the ammonium tungstate solution is filtered. The filtrate should have but a slight tinge of yellow col'or'and for convenience, this may be termed solution A. Half of this ammonium tungstate solution is then placed in aporcelain evaporating dish and C. P. HCL is per- -mitted to run into the same from fine constrictions with a constant stirring until the solution gets turbid and very fine crystals float around in the same, or reaches a point where the solution 'is almost neutral. This solution is then permitted to cool for at least ten hours and the crystals allowed to settle. After washing the crystals several times, they are filtered through a Buechuer funnel and dried in a nickelpan in a furnace heated to about 300 C. to lOQ" C., long enough for most of the ammonia to be driven off. This may be called mixture A.

The other half of solution -A. is heated to a-temperature of about to C. and slowly introduced into a vessel containing a boiling mixture of about three parts nitric acid and four parts hydrochloric acid and fourparts water. A current of steam ,is injected-into this mixture while solution A is being introduced, and a precipitate of tungsten oxide is obtained which is finally removed and filtered and washed with hot distilled water and then dried out into the form of a fine yellow powder of tungsten oxide. This may be called mixture B.

Instead of using a solution of ammonium tungstate, in some cases I prefer to precipitate the tungsten oxide from .the sodium tungstate solution.

Equal portions of the crystalline mixture A and the. amorphous mixture 3" are weighed out and the two thoroughly mixed for at least. two hours in a. porcelain ballmill. The mixture is then placed into a large porcelain evaporating dish and a solution of sodium vanadate added of such a strength as to introduce about 25%to 2.0% of Vana- Liuin into the tungsten oxide. Also a solution of potassium silicate is added of such a strength so as to introduce about 50% silicon into the oxides. E then add 'arl'ion, or a caramel solution of specific gravity i.l in such amounts as to contain a carbon equivalent sufliciently large to reduce the above vanadium and silicon. Thie mixture is then thoroughly slurried and mixed so as to make a thoroughly homogeneous mass after which the same is dried out in a silicate dish and thoroughly heated in a furnace, either gas or electric, for a period of about half an hour, at about l000 C. In some cases I also introduce thorium nitrate of such an amount as to give one to two percent thorium content in the tungsten oxide. If I do this, amount of caramel solution must be increased so that its carbon content will take care of the reduction of the amount of thorium nitrate introduced.

The dried mixture of tungsten oxides, carbon, vanadium oxide, silica and thoria is screened through an eighty-meshsieve and is then ready for reduction. This mixture is then reduced in a convenient way in a gas or electric furnace by first heating the same in nickel boats at a temperature of about 600 to 650 C. for twoto three hours. and then at a temperature of 900 to 950 C. for five to six hours in hydrogen. This will produce metal of a dark gray color. having:

a weight of tiirty to forty grams per cubic inch. The ma tcrial may also be reduced in other ways. such for example with carbon. I prefer. however. to use hydrogen bubbled through aqua ammonia. instead of introducing" the silicon and thorium into the oxide as a nitrate. I may also introduce the silicon and thorimn in elementary form after the tungsten oxide has been reduced to tungsten metal. The resultant mixture of the above elements in fine powderform. after being sifted through a QOO-mesh sieve and thoroughly mixed. is converted into adherent and coherent bodies by processes'well known in the art, such as by pressing the mixture in a suitable mould on a hydraulic, press. into the form of a slug. and then baking or sintering the body in hydrogen or in an inert atmosphere. After sintering these slugs at about 85% to 90% of their fusing current, they maybe worked down into the form of rod or sheet, either by swa-ging or rolling. The mechanical process of rolling and swag,- ing is carried out at a yellow heat at first, and at a red heat after the bar nave been reduced to the smaller Lift: the alloy has been formed into sheet or rod or any desired shape, face plates are punched from the same, or if round rod is produced, discs may be sliced oil the rod by means of a carborundum or alundum cutting Wheel revolving at high speeds.

One side of the face plate thus formed is then coated with a thin. uniform layer of copper-nickel alloy. This is accomplished by placing the face plate upon a suitable nichrome form or plate and then placing a thin sheet of copper-nickel alloy of the same form as the face plate and of about 0.003 to 0.004 in thickness, upon the face plate. The nichrome holders are then placed in an elec* tric or gas furnace in. a hydrogen atmosphere. and heated to a temperature of about .250 to 18-50 C. After the holders, together with the face plates, attain the above tem perature, the thin discs soften and alloy with the particular composition of which the face plates are composed and uniformly spread over the surface. forming a thin layer. The face plates with. the thin layer of coppernickel alloy are; then placed in a cooling chamber and. permitted to cool.

Becauseof the particular composition that I have produced, the nickel alloy penetrates the face plates and-spreads uniformly over the surface without drawing up into globules. composition of the copper nickel alloy is about 90% copper and 10% nickel.

The resultant product, consisting of a face plate of the above: alloy which has been coated with copper-niche as outlined above. may now be: welded or joined to any base metal hacking material by the well known brazing operations. using any suitable intermediate layer of brazing; material. depending upon the particular composition of the backing.

As changes of operation could be made Within. the scope of my invention, it is intended that all matter contained in the above descriotion shall be interpreted as illustrative and not in a limiting sense.

Having now described my invention. What I claim as new and desire; to secure by Letters Patent is: I

1. A face plate of a hard. compact alloy of tungsten. vanadium, silicon and thorium. said vanadium. silicon and thorium constituting but a small part of said alloy 2. -& face plate comprising a disc of hard, compact alloy of tungsten, vanadium and silicon, the tungsten com-prising 90 per cent 1 or more of-the alloy.

3. A face plate comprising a disd of a, hard, compact alloy of tungsten, vanadium and silicon; the tungsten contentbeing 75 per cent or more of the alloy containing a greater proportion of vanadium than of silicon.

In testimony whereof I hereunto afiix my signature.

CLELENS A. LAISE. 

